Multilayer electrometric material containing active chemical substance, and uses thereof

ABSTRACT

The present invention relates to a multilayer material made from elastomers and containing one or more active substances dispersed in the form of droplets, and also to its uses, especially as a glove, a finger stall, a condom, a tape or dressings.

The present invention relates to a multilayer material made fromelastomers and comprising at least one layer containing one or moreactive substances dispersed in the form of droplets, and also to itsuses, especially as a glove, a finger stall or condoms.

SUMMARY OF THE DRAWINGS

FIG. 1 shows a material with three separate layers L₁, L₂ and L_(3.)

FIG. 2 shows a material with three separate layers L₁, L₂ and to and atextile weft.

FIG. 3 shows a multilayer material produced by Example 2.

The various elastomeric materials usually used in the medical orparamedical field (especially hygiene) may be modified so as to becombined with active chemical substances, which have a protectiveeffect, during the use of this material (gloves, finger stalls, condomsand various tapes and dressings). Specifically, not only in the cases ofexamination or surgery or in odontology, but also for protection againstpathogens such as, for example, bacteria, viruses and fungal spores, arupture or occasionally even simply the pores or a crack in theelastomeric membrane can result in contamination of the wearer of thesaid material by pricking with syringes, suture needles, trocars, bonesplinters, etc.

Thus, elastomeric films in which are uniformly dispersed, in the form ofliquid droplets, active chemical substances such as disinfectants formedical use, have already been proposed, especially in patentapplication EP-A-0 981 573. Such materials are generally in the form ofthree separate layers L₁, L₂ and L₃ as represented by FIG. 1 in whichthe layers L₁, and L₃ are outer barrier layers and L₂ represents anintermediate lava containine the active chemical substance(s) dispersedin the form of droplets.

In these materials, the liquid containing the active chemicalsubstance(s) is uniformly and stably dispersed in the form of dropletsand is thus available in the event of accidental rupture of the outerprotective layer L₁ or L₃.

Unfortunately, such films do not always have the desired performancequalities. Firstly, the amount of active chemical substances coming intocontact with the sharp object is quite often insufficient to ensure thedesired properties, and secondly, the fluid is only placed in contactrather than expelled onto the blunt object, thus ensuring only partialwetting of the said object, resulting in low efficacy of devices of thistype. This last point is all the more important since the geometry ofthe sharp object is often complex (hollow, bevelled needles, etc.).

It is thus in order to overcome these major problems that, in the courseof its research, the Applicant has discovered, surprisingly, that thefinal characteristics of the multilayer material, such as the amount ofactive substance deposited on the blunt object and the speed ofexpulsion of the droplets of active substance, depend on the combinationof the intrinsic characteristics of each of the constituent layers ofthe material.

According to the present invention, the term “intrinsic characteristics”means the mechanical characteristics (breaking stress and elasticconstant) and size characteristics (thickness) of the formulatedelastomers constituting each layer, and also, for the intermediate layerL₂, the degree of filling and the size of the droplets. In thisinvention, the intrinsic characteristics of each of the layers areadjusted by considering the multilayer material taken as a whole.

The inventors thus set themselves the aim of providing a multilayerelastomeric material containing at least one active substance, which isespecially capable of being used in the medical or paramedical field forthe manufacture of protective devices with improved performancequalities as regards the amount of active substance coming into contactwith a blunt object in the event of perforation of the said device, andalso as regards the speed with which this active substance comes intocontact with the said blunt object compared with similar materials ofthe prior art.

A first subject of the invention is thus a multilayer elastomericmaterial comprising at least two outer barrier layers L₁ and L₃,respectively having a breaking stress σ₁ and σ₃ and a thickness e₁ ande₃, enclosing at least one intermediate layer L₂ consisting of anelastomeric matrix comprising at least one dispersion of droplets of atleast one composition containing at least one active substance, the saidintermediate layer L₂ having a breaking stress σ_(2Tot) and a thicknesse₂, characterized in that the mean diameter of the said droplets isgreater than or equal to 10 μm and that the said material satisfies thefollowing double inequality (1):(σ_(2Tot) ·e ₂)<(σ₁ ·e ₁) and (σ_(2Tot) ·e ₂)<(σ₃ ·e ₃)  (I)

-   -   in which inequality:    -   σ_(2Tot) represents the breaking stress of the charged        elastomeric material constituting the layer L₂,    -   σ₁, σ₃, e₁, e₂ and e₃ are as defined above.

In the inequalities defined above, σ_(2Tot) is a function of the volumefraction φv of the droplets incorporated into the layer L₂, and of theintrinsic characteristics of the elastomeric material constituting thematrix (σ₂). In this regard, φv can, of course, be adjusted to satisfythe above inequalities concerning the breaking stress σ_(2Tot.)

By virtue of these particular characteristics, and when a pressure isexerted on the material in accordance with the invention with a sharpobject, the intermediate layer L₂ gives way before the outer layers L₁and L₃ and the droplets are expelled onto the sharp object after theouter barrier layer (L₁ and/or L₃) has been ruptured.

The inventors have in fact demonstrated that the rupture of theconstituent layers of a multilayer material essentially depends on theresistance to the cutting or piercing force of each of the layers, whichis proportional to the product of the breaking stress multiplied by thethickness for each of the layers. The breaking stress of theintermediate layer furthermore depends on the amount of compositioncontaining the active substance included in this layer (volume fractionof liquid φv).

According to the invention, the breaking stresses σ₁, σ₂, σ_(2Tot) andσ₃ are measured experimentally using a Zwick tensile testing machine, ata speed of 500 mm/minute and with specimens H2 according to standard NFEN455-2.

According to one advantageous embodiment of the invention, the product(σ_(2Tot)·e₂) corresponds to the following double condition (II):(σ_(2Tot) ·e ₂)≦(σ₁ ·e ₁)/2 and (σ_(2Tot) ·e ₂)≦(σ₃ ·e ₃)/2  (II)

in which σ₁, σ_(2Tot), σ₃, e₁, e₂ and e₃ have the same meanings as thosegiven above.

The breaking stresses σ₁, σ₂ and σ₃ of each of the layers of thematerial in accordance with the invention, which may be identical ordifferent, preferably range between 0.1 and 100 MPa and even morepreferably between 5 and 40 MPa.

The thicknesses e₁, e₂ and e₃ of each of the layers of the material inaccordance with the invention, which may be identical or different,preferably range between 25 and 500 μm approximately, this thicknessbeing chosen as a function of the intended use of the said material.

As non-limiting examples, when the material in accordance with theinvention is intended to be used for manufacturing condoms, then thethickness of each of the layers is about 25 μm; when it is used formanufacturing surgical gloves, then the thickness of each of the layersis about 100 μm and when it is used for manufacturing protective gloves,for example household gloves or refuse collectors' gloves, then thethickness of each of the layers is about 500 μm.

According to one preferred embodiment of the material in accordance withthe invention, the mean diameter of the droplets dispersed in the layerL₂ is preferably between about 10 and 100 μm approximately.

Preferentially, the inventors have also demonstrated that the expulsionof the composition containing the active substance onto a blunt objectperforating one of the two barrier layers L₁ or L₃ is also improved as afunction of the viscoelasticity of the constituent materials of eachlayer, and more particularly of their elastic constant (E), i.e. E₁, E₂and E₃, respectively.

Thus, according to one advantageous embodiment of the invention, theelastic constant of the constituent material of the intermediate layerL₂ is greater than that of the barrier layers L₁ and L₃ (E₁ and E₃),i.e. E₂>max (E₁, E₃).

According to the invention, the elastic constants of each of the layersL₁, L₂ and L₃, i.e. E₁, E₂ and E₃, respectively, are preferably between0.1 and 50 MPa and even more preferably between 0.1 and 10 MPa for thelayers L₁ and L₃ and between 0.5 and 50 MPa for the layer L₂; the valuesof E₁ and E₃ being identical or different.

According to the invention, the elastic constants are measured using aviscoanalyser of DMTA type (Dynamical Thermal Analysis such as themachine VA2000 from the company Metravib), which is capable ofevaluating, in usual temperature ranges, the viscoelasticcharacteristics of the materials under consideration, at a frequency of1 Hz (driven in the linear viscoelastic range), in traction-compressionmode, according to the method described in standard NF EN ISO 527-3.

According to the invention, the elastomer(s) constituting the outerbarrier layers L₁ and L₃ and also the intermediate layer L₂ arepreferably chosen from natural rubber, polybutadiene, polyisoprene,polychloroprene, polyurethane, acrylic polymers or copolymers, siliconeelastomers, SBR (Styrene Butadiene Rubber) copolymers, SBS (StyreneButadiene Styrene) copolymers, isobutene-isoprene copolymers such asbutyl rubber, NBR (Nitrile Butadiene Rubber) copolymers, x-NBR(carboxylated Nitrile Butadiene Rubber) copoymers, SIS (Styrene IsopreneStyrene) copolymers, SEBS (Styrene Ethylene Butylene Styrene) copolymersand blends thereof; it being understood that the nature of theelastomer(s) constituting each of the said layers may be identical to ordifferent from each other. According to the invention, SIS and SEBS arepreferred.

The characteristics of the elastomers (molar mass and crosslinkingdensity (chemical and/or physical) are selected as a function of thefinal characteristics desired for the layers L₁ and L₃ and for the layerL₂, with the proviso that they satisfy, of course, the definitions givenabove.

In addition to the elastomers defined above, at least one of the barrierlayers L₁ and L₃, and/or the intermediate layer L₂, may also contain oneor more plasticizer(s) or flexibilizer(s) whose chemical nature andcontent are compatible with the intrinsic characteristics of thematerial as defined above.

When they are used, these plasticizers are preferably chosen frommineral oils, among which mention may be made especially of liquidparaffins, but may also be chosen from naphthalene-based oils oraromatic oils or mixtures of these products.

When they are used, the plasticizer(s) preferably represent(s) from 5 to500 parts per 100 parts of elastomer constituting the layer in whichthey are present.

It should be noted that the chemical nature, the composition or thethickness of the layer L₁ is not necessarily equivalent to that of thelayer L₃.

Finally, each layer L₁ or L₃ may, as a variant, result from thesuperposition of two or more sublayers of equivalent or non-equivalentchemical nature. The intrinsic characteristics of the layer L₁ or L₃will then be those measured on the whole layer.

The intermediate layer L₂ serves as a matrix for the droplets ofcomposition containing the active chemical substance(s) used.

According to the invention, the nature of this active substance may bechosen as a function of the properties that it is desired to give to theintermediate layer L₂. This active chemical substance may be chosenespecially from anticorrosion agents, lubricants, chemical markers,phase-change products, energetic-particle (radiation) decelerators,agents with disinfecting power, odoriferous agents or moisturizers, dyesfor detecting cuts, metallic particles, and mixtures thereof.

When the active chemical substance is a product with disinfecting power,it is preferably chosen from substances capable of causing a virtuallyinstantaneous denaturation of proteins by simple contact, either bychemical reaction or by a physicochemical effect such as a modificationof the surface tension. Among such substances, mention may be madeespecially of biocides, such as quaternary ammoniumns and moreparticularly dimethyldidecylammonium chloride and benzalkonium chloride,biguanides such as water-soluble salts of chlorhexidine, for instancechlorhexidine digluconate, phthalaldehyde, phenolic derivatives such ashexachlorophene or benzylic derivatives, formaldehyde, nonionicsurfactants comprising at least one polyoxyethylene sequence such asoctoxynol (Triton®X100), hexamidine, iodinated polyvinylpyrrolidonecompounds, nonionic surfactants with virucidal activity, sodium andpotassium dichromates and hypochlorites, and mixtures thereof.

In addition to the active chemical substance(s), the composition in theform of droplets may also contain one or more diluents for dissolvingthe said active chemical substance(s).

When it used, this diluent may be chosen especially from polyols andpreferably from glycerol, ethylene glycol, polyethylene glycols that areliquid at room temperature or a temperature close to room temperature(between 20 and 30° C. approximately) and with a molar mass of between62 (ethylene glycol) and 750 daltons (polyethylene glycol: PEG 750) andmixtures thereof, and also from any other compound that is compatiblewith the active chemical substance(s) used.

In addition, the composition in the form of droplets may also containone or more additives for adjusting the final characteristics of themixture, for instance dyes, surfactants or thickeners.

The composition in the form of droplets and containing the activesubstance may be in liquid (in the form of an emulsion), gelled form orcontain crystalline portions (microspheres). When this composition is inthe form of microspheres, they may also be coated with a thin film ofprotective polymer (microcapsules).

According to one particular embodiment of the invention, theintermediate layer L₂ may be formed from a superposition of two or moreintermediate sublayers each comprising a dispersion of droplets, thenature of the active substances contained in each of the said sublayersbeing identical or different from one sublayer to another. In this case,the intrinsic characteristics of the layer L₂ will then be thosemeasured on the whole layer.

According to another particular embodiment of the invention, theintermediate layer L₂ is formed by a single layer containing adispersion of droplets containing active chemical substances that aredifferent from one droplet to another.

Each of the layers constituting the elastomeric material in accordancewith the invention may also contain other adjuvants conventionally usedin the polymer industry, for instance antistatic agents, lubricants,antioxidants, colorants, processing agents or adhesion promotersdepending on the particular properties that it is desired to impartthereto, provided, of course, that these adjuvants are compatible witheach other and with the intrinsic characteristics of the said materialas defined above.

According to one variant of the invention, the rnultiplayer material maybe reinforced with an elastic textile weft of natural or syntheticorganic fibres thus serving as a support for one of the two barrierlayers L₁ or L₃. When the textile weft is adjacent to the barrier layerL₁, this type of multilayer material may be represented by FIG. 2.

The link between the various constituent layers of the material inaccordance with the invention may optionally be provided by a bondingagent or by a chemical or physicochemical modification of any one of thelayers. However, such a treatment has no influence on the finalcharacteristics of the material.

According to the invention, the expression “chemical modification” meanseither grafting or chemical attack, and “physicochemical modification”means bombardment of the surface of the film with ions, electrons orphotons.

The multilayer elastomeric material in accordance with the invention mayespecially be in the form of gloves, finger stalls, condoms, tapes,dressings, etc.

A subject of the present invention is thus also the use of at least onemultilayer elastomeric material as defined above for the manufacture ofprotective elastomeric articles such as gloves, finger stalls, condoms,tapes or dressings.

The manufacture of the multilayer material as defined above may beperformed according to a process of successive dipping and evaporationoperations on a form corresponding to the use intended for the saidmaterial, in organic solutions or aqueous dispersions (latex) of thechosen elastomer(s) so as to successively form the layers L₁, L₂ and L₃,the formation of the layer L₂ being performed, for example, by processesconsisting:

-   -   either in preparing a stable emulsions formed from droplets of a        liquid composition containing the active chemical substance(s)        in a dissolution of the elastomer in a volatile solvent, as        described especially in patent application EP-A-0 981 573;    -   or in preparing a dispersion of the said droplets in gelled        form, or crystallized form (microspheres) in a dissolution of        the elastomer in a volatile solvent, as described in patent        application EP-A-771 837. Optionally, the microspheres may be        coated with a thin film of protective polymer (microcapsules);    -   or in depositing the droplets, for example, in the form of        microspheres or microcapsules onto the layer L₁ and/or L₃, and        then in covering the said droplets with an elastomer, either in        the form of a solution thereof in an organic solvent, or in the        form of an aqueous dispersion (latex), or in solid form.

During this process, each dipping operation is followed by a period ofevaporation, generally in a thermostatically regulated oven, duringwhich the solvent or the water is removed.

When the multilayer material in accordance with the present inventioncomprises a support made of textile material, then the first dippingoperation is performed with a porcelain form covered with a textileweft.

Besides the preceding arrangements, the invention also comprises otherarrangements that will emerge from the description that follows, whichrefer to examples for preparing multilayer elastomeric materials inaccordance with the invention, and also to a comparative example forpreparing a multilayer material not in accordance with the invention.

It should be clearly understood, however, that these examples are givensolely for the purposes of illustrating the subject of the invention, ofwhich they do not in any way constitute a limitation.

EXAMPLE 1 Preparation of a Multilayer Elastomeric Material in AccordanceWith the Invention

This example describes the preparation of a multilayer material madeentirely from synthetic elastomer in solvent medium.

1) Preparation of the Multilayer Material

A first bath of elastomer in a solvent (cyclohexane) consisting of 20%by weight (relative to the solids) of a mix of SEBS copolymer sold underthe trade name Kraton® G1652, by the company Kraton® Polymers, and of amineral oil (Primol® 352, Esso company) used as plasticizer, isprepared. The elastomer/plasticizer mass proportions in this mixture are100:30. This bath is used to make the barrier layers L₁ and L₃.

Moreover, and according to the process described in patent applicationEP-A-981 573, a bath of elastomer (SEBS: Kraton® G1652 at 20% by weightof solids in cyclohexane) containing a dispersion of droplets of activesubstance (benzalkonium chloride dissolved in ethylene glycol, in massproportions of 1:9) stabilized with a particulate organic stabilizer,which is a polybutadiene-poly(ethylene oxide) diblock copolymer in aproportion of 5 parts per 100 parts of solution of benzalkonium chloridein ethylene glycol, is prepared.

The mean droplet diameter (measured using a optical microscope) in thisdispersion is 30 μm. The volume fraction of the droplets φv is 0.5(relative to the solids after mixing with the elastomer dissolved incyclohexane).

The multilayer material is then prepared by successive dippingoperations of a porcelain form in the following manner:

1) formation of the barrier layer L₁: two successive dipping operationsin the first elastomer bath;

2) formation of the intermediate layer L₂: three successive dippingoperations in the second elastomer bath containing the dispersion of theactive substance; and then

3) formation of the barrier layer L₃: two successive dipping operationsin the first elastomer bath;

it being understood that each dipping step is immediately followed by astep of evaporating off the cyclohexane, first in the open air and thenin an oven at a temperature of 40° C., until the solvent has completelyevaporated off.

A multilayer material consisting of two identical barrier layers L₁ andL₃, each 175 μm thick, and of an intermediate layer L₂, 200 μm thick,containing a dispersion of droplets of benzalkonium chloride (thethicknesses are measured with a micrometric comparator) is thusobtained.

2) Characterization of the Multilayer Material

In order to determine the intrinsic characteristics of each of thelayers constituting this material, two separate elastomeric films areprepared by:

-   -   firstly dipping a first porcelain form in the first elastomer        bath (according to the technique described above in Step 1) for        the preparation of the multilayer material) so as to produce a        monolayer material consisting only of a layer L₁;    -   secondly, dipping a second porcelain form in the second        elastomer bath (according to the technique described above in        Step 2) for the preparation of the multilayer material) so as to        produce a monolayer material consisting only of a layer L₂

The separate layers L₁ and L₂ thus prepared were then studied in orderto measure their intrinsic characteristics.

For each of the layers L₁ and L₂, the breaking stresses were measuredusing a tensile testing machine (Zwick) on specimens of H2 type, at aspeed of 500 mm/minute, in accordance with standard NF EN455-2.

The elastic constants are measured using a VA2000 viscoanalyser(Metravib R. D. S, Limonest, France) on rectangular specimens of thelayers L₁ and L₂, 20×50 mm in size, in traction-compression mode, inaccordance with the method described in standard NF EN ISO 527-3.

The amount of active chemical substance expelled onto a needle duringperforation of the glove is evaluated on the multilayer material, bymeans of a standardized test consisting in:

-   -   cutting the multilayer material along a vertical cutting plane        L₁, L₂, L₃, under liquid nitrogen,    -   backing the cutting plane onto a glass slide,    -   placing the assembly in the field of a reflecting microscope        (Questar),    -   pricking the multilayer material with a hollow needle 0.7 mm in        diameter, filled with ultrapure water, at a pricking speed of 15        cm/s,    -   measuring the speed of expulsion of the benzalkonium chloride        under the field of the microscope using a video camera,    -   analytically assaying the amount of benzalkonium chloride        deposited on the needle using a capillary electrophoresis        device.

3) Results

The characteristics of the multilayer material are summarized in Table Ibelow:

TABLE I Breaking stress σ Elastic constant E Product (σ · e) Layers (inMpa) (in Mpa) (in Pa · m) L₁ 25 2 4375 L₂     9 ^(a) 7 1800 L₃ 25 2 4375^(a) the value given is the breaking stress of the elastomeric layercharged with benzalkonium chloride.

The amount of benzalkonium chloride deposited on the needle is evaluatedat 1 μg; the speed of expulsion is estimated as 5 m/s.

EXAMPLE 2 Preparation of a Multilayer Material in Accordance With theInvention

The aim of this example is to illustrate the preparation of a “hybrid”material made from natural rubber and synthetic elastomer via a waterand solvent mixed process.

1) Preparation of the Multilayer Material

In this case, the said material is obtained by successive dippingoperations of a porcelain form in an aqueous dispersion of naturalrubber (latex) to form the two barrier layers L₁ and L₃ and in asolution of synthetic elastomer in cyclohexane, the said solutioncontaining a dispersion of active substance to form the layer L₂.

a) Preparation of the Barrier Layers L₁ and L₃

The barrier layers are formed by superposition of two sublayers.

The first sublayer is formed by dipping (twice) a porcelain form in abath of nitrile latex (x-NBR: butadiene-acrylonitrile-methacrylic acidcopolymer, sold by the company Polymer Latex) at 50% (solids) alsocomprising 10% zinc oxide, 2% zinc diethyldithiocarbamate (ZDEC) and1.5% sulphur.

The second sublayer is formed by dipping (once) the form in a mixture ofnatural latex (NR) and of nitrile latex x-NBR, in a mass proportion of75:25. The nitrile latex is the same as that used above to form thefirst sublayer. The natural latex (Heveatex) is formulated with 1%sulphur and 0.8% ZDEC.

The solids content of the nitrile latex/natural latex mixture is about45%.

b) Formation of the Layer L₂

This is prepared as described above in Example 1.

A multilayer material consisting of two identical barrier layers L₁ andL₃ each 250 μm thick and of an intermediate layer L₂, 200 μm thick,containing a dispersion of droplets of benzalkonium chloride, is thusobtained.

Each dipping step is immediately followed by a step of evaporating offthe water, first in the open air and then in an oven at a temperature of40° C. (evaporation of the cyclohexane for the layer L₂) or at 60° C.(evaporation of the water for the layers L₁ and L₃), until thecylcohexane and the water have completely evaporated off.

The final multilayer material is then vulcanized at 80° C. for 2 hours.

The structure of the final material as produced according to thisexample is represented in FIG. 3.

The multilayer material thus prepared is then characterized according tothe methods described above in Example 1.

The characteristics obtained are given in Table II below:

TABLE II Breaking stress σ Elastic constant E Product (σ · e) Layers (inMpa) (in Mpa) (in Pa · m) L₁ 12 3 3000 L₂     9 ^(a) 7 1800 L₃ 12 3 3000^(a) the value given is the breaking stress of the elastomeric layercharged with benzalkonium chloride.

The amount of benzalkonium chloride deposited on the needle after theperforation test under the conditions described above in Example 1 isevaluated as 0.6 μg. The speed of expulsion is evaluated as 3 m/s.

COMPARATIVE EXAMPLE 3 Preparation of a Multilayer Material Not inAccordance With the Invention

This counterexample illustrates the preparation of a multilayer materialbased on synthetic elastomers of SEBS type but whose characteristics donot correspond to the double inequality (1) as defined according to thepresent invention.

1) Preparation of the Multilayer Material

The multilayer material is entirely made from dissolutions of SEBS incyclohexane. The various elastomer baths used to make the layers L₁ andL₃ are as follows:

-   -   Barrier layers L₁ and L₃: elastomer bath consisting of 20% by        weight (relative to the solids) of a mixture of SEBS copolymer        sold under the trade name Kraton® G1652 by the company Kraton        Polymers, and of a mineral oil (Primol® 352, Esso company) used        as plasticizer, dissolved in cyclohexane. The        elastomer/plasticizer mass proportions in this mixture are        100:30.

Intermediate layer L₂: elastomer bath consisting of 20% by weight(relative to the solids) of a mixture of SEBS copolymer sold under thetrade name Kraton® G1654 by the company Kraton® Polymers, and of amineral oil (Marcol® 82, Esso company) used as plasticizer, dissolved incyclohexane. The elastomer/plasticizer mass proportions in this mixtureare 100:50. This elastomer bath contains a dispersion of droplets ofactive substance (benzalkonium chloride dissolved in ethylene glycol, inmass proportions of 1:9) stabilized with a particulate organicstabilizer, which is a polybutadiene-poly(ethylene oxide) diblockcopolymer in a proportion of 5 parts per 100 parts of solution ofbenzalkonium chloride in ethylene glycol.

The mean droplet diameter (measured using an optical microscope) in thisdispersion is 30 μm. The volume fraction of the droplets φv is 0.3(relative to the solids content after mixing with the elastomerdissolved in cyclohexane).

A multilayer material consisting of two identical barrier layers L₁ andL₃ each 150 μm thick and of an intermediate layer L₂, 250 μm thick,containing a dispersion of droplets of benzalkonium chloride (thethicknesses are measured using a micrometric comparator) is thusobtained.

The multilayer material thus prepared is then characterized according tothe methods described above in Example 1.

The characteristics obtained are given in Table III below:

TABLE III Breaking stress σ Elastic constant E Product (σ · e) Layers(in Mpa) (in Mpa) (in Pa · m) L₁ 25 2 3775 L₂    16 ^(a) 1 4000 L₃ 25 23775 ^(a) the value given is the breaking stress of the elastomericlayer charged with benzalkonium chloride.

A material whose intrinsic characteristics do not satisfy the doubleinequality (I) defined above, since the product (σ_(2Tot).e²) of theintermediate layer L₂ is greater than that of each of the barrier layersL₁ and L₃, is thus obtained.

The amount of benzalkonium chloride deposited on the needle after theperforation test under the conditions described above in Example 1 isevaluated as 0.1 μg, which corresponds to an amount that is about 10times less than that of Example 1. The speed of expulsion is evaluatedas 1 m/s, which corresponds to a speed that is about 5 times slower thanthat of Example 1.

This set of results shows that the materials in accordance with theinvention, i.e. the multilayer materials in which the intrinsiccharacteristics of each of the layers satisfy the double inequality (I)as defined above, show improved performances as regards the amount ofactive substance coming into contact with a needle in the event ofperforation of the said material, and also as regards the speed withwhich this active substance comes into contact with the said needle.

1. A multilayer elastomeric material comprising: at least two outermostelastomeric barrier layers L₁ and L₃, respectively having a breakingstress σ₁ and σ₃, a thickness e₁ and e₃, and an elastic constant E₁ andE₃, enclosing at least one intermediate layer L₂ consisting of anelastomeric matrix comprising at least one dispersion of droplets of atleast one composition containing at least one active substance, theintermediate layer L₂ having a breaking stress σ_(2Tot), a thickness e₂,and an elastic constant E₂, wherein the mean diameter of the droplets isat least 10 μm and that the material satisfies the following doubleinequality (I):(σ_(2Tot) ·e ₂)<(σ₁ ·e ₁) and (σ_(2Tot) ·e ₂)<(σ₃ ·e ₃)  (I) in which:σ_(2Tot) represents the breaking stress of the charged elastomericmaterial constituting the layer L₂, and σ₁, σ₃, e₁, e₂ and e₃ are asdefined above.
 2. The material according to claim 1, wherein the product(σ_(2Tot)·e₂) corresponds to the following double condition (II):(σ_(2Tot) ·e ₂)≦(σ₁ ·e ₁)/2 and (σ_(2Tot) ·e ₂)≦(σ₃ ·e ₃)/2  (II) inwhich σ₁, σ_(2Tot), σ₃, e₁, e₂ and e₃ are as defined in claim
 1. 3. Thematerial according to claim 1, wherein the breaking stresses σ₁, σ₂ andσ₃ of each of the layers of the material, which may be identical ordifferent, range between 0.1 and 100 MPa.
 4. The material according toclaim 1, wherein the thicknesses e₁, e₂ and e₃ of each of the layers ofthe material, which may be identical or different, range between 25 and500 μm.
 5. The material according to claim 1, wherein the mean diameterof the droplets is between 10 and 100 μm.
 6. The material according toclaim 1, wherein the elastic constant, E₂, of the constituent materialof the intermediate layer L₂ is greater than each of the elasticconstants, E₁ and E₃, of the barrier layers L₁ and L₃, respectively. 7.The material according to claim 6, wherein the elastic constants E₁, E₂and E₃ of each of the layers L₁, L₂ and L₃, respectively, are between0.1 and 50 MPa, and the values of E₁ and E₃ being identical ordifferent.
 8. The material according to claim 7, wherein the elasticconstants of the layers L₁ and L₃, which may be identical or different,are between 0.1 and 10 MPa and the elastic constant of the layer L₂ isbetween 0.5 and 50 MPa.
 9. The material according to claim 1, whereinthe elastomer(s) constituting the barrier layers L₁ and L₃ and also theintermediate layer L₂ are chosen from natural rubber, polybutadiene,polyisoprene, polychloroprene, polyurethane, acrylic polymers orcopolymers, silicone elastomers, SBR (Styrene Butadiene Rubber)copolymers, SBS (Styrene Butadiene Styrene) copolymers, SEBS (StyreneEthylene Butylene Styrene) copolymers, isobutene-isoprene copolymers,NBR (Nitrile Butadiene Rubber) copolymers, x-NBR (carboxylated NitrileButadiene Rubber) copolymers, SIS (Styrene Isoprene Styrene) copolymersand blends thereof.
 10. The material according to claim 9, wherein theelastomers are chosen from SIS and SEBS.
 11. The material according toclaim 1, wherein at least one of the barrier layers L₁ and L₃, andoptionally the intermediate layer L₂, also contains one or moreplasticizer(s) or flexibilizer(s).
 12. The material according to claim11, wherein the plasticizer(s) represent(s) from 5 to 500 parts per 100parts of elastomer constituting the layer in which they are present. 13.The material according to claim 1, wherein each layer L₁ or L₃ resultsfrom the superposition of two or more sublayers of equivalent ornon-equivalent chemical nature.
 14. The material according to claim 1,wherein the active chemical substance is chosen from anticorrosionagents, lubricants, chemical markers, phase-change products,energetic-particle (radiation) decelerators, agents with disinfectingpower, odoriferous agents or moisturizers, dyes for detecting cuts,metallic particles, and mixtures thereof.
 15. The material according toclaim 14, wherein the active chemical substance is chosen from biocides,biguanides, phthalaldehyde, phenolic derivatives, formaldehyde, nonionicsurfactants comprising at least one polyoxyethylene sequence,hexamidine, iodinated polyvinylpyrrolidone compounds, nonionicsurfactants with virucidal activity, sodium and potassium dichromatesand hypochlorites, and mixtures thereof.
 16. The material according toclaim 1, wherein the composition in the form of droplets also containsone or more diluents for dissolving the active chemical substance(s).17. The material according to claim 1, wherein the dispersion ofdroplets is in liquid or gelled form or contains crystalline parts. 18.The material according to claim 1, wherein the intermediate layer L₂ isformed from a superposition of two or more intermediate sublayers eachcomprising a dispersion of droplets, the nature of the active substancescontained in each of the sublayers being identical or different from onesublayer to another.
 19. The material according to claim 1, wherein theintermediate layer L₂ is formed by a single layer containing adispersion of droplets containing active chemical substances that aredifferent from one droplet to another.
 20. A glove, comprising theelastomeric material of claim
 1. 21. A finger stall, comprising theelastomeric material of claim
 1. 22. A condom, comprising theelastomeric material of claim
 1. 23. A tape, comprising the elastomericmaterial of claim
 1. 24. A dressing, comprising the elastomeric materialof claim 1.